The present invention relates to an electron multiplier device which can emit secondary electrons, and more particularly to such a device which can be used for a photomultiplier tube.
A prior electron multiplier device is known in which conventional dinodes of the Venetian-blind type are used and in which electrons are multiplied by a plurality of such dinodes which are closely arranged within a relatively narrow space.
FIG. 1 shows a cross-sectional view of a part of the electron multiplier device consisting of dinodes of the conventional venetian-blind type.
In FIG. 1, stages "i" and "i+1" of the electron multiplier device consisting of a plurality of mesh-and-dinode stages which are stacked are after another are shown in detail. Mi in FIG. 1 indicates the i-th mesh arranged orthogonally to the electron path. Dyi indicates the i-th dinode. Mi+1 indicates the "i+1"-th mesh. Dyi +1 --; and indicates the "i+1"-th dinode.
The "i+1"-th dinode is inclined in the opposite direction to the i-th dinode.
Dinodes with opposite inclination angles and the corresponding meshes are alternately arranged to form an electron multiplier device.
The meshes are made of metal plates. Each metal plate is masked and selectively etched by a photoetching process.
The dinode of Venetian-blind type is made by press work, and this type of dinode is used as a secondary electron emission electrode.
Mesh Mi is connected to dinode Dyi and they are kept at potential Vi. Mesh Mi+1 is connected to dinode Dyi+1 and they are kept at potential Vi+1.
Secondary electrons emitted from dinode Dyi responding to the electrons incident on dinode Dyi are incident on inclined dinode Dyi+1 in the next stage, and then they are multiplied there.
If the number of dinodes in the electron multiplier device consisting of a plurality of dinodes of Venetian-blind type is increased, resolution at an arbitrary point on the incident plane can be improved to some extent.
Secondary electrons emitted from dinode Dyi are once decelerated by the rear surface of the adjacent dinode leaf and accelerated by mesh Mi+1--; in the next stage. Secondary electrons are then incident on dinode Dyi+1. Deceleration in the above process causes the electron transit time to be increased and its variation to be enhanced.
The electron transit time and its variation are proportional to the dimensions of the electrodes. The dinode sizes and the gaps between adjacent dinode leaves are to be minimized to reduce the electron transit time and its variation.
However, the accuracy of the dimensions in the dinodes finished by metal work is limited. It is thus impossible for the electron transit time and its variation to be reduced beyond the limit, and also for resolution at an arbitrary point on the dinode to be greatly improved.
The objective of the present invention is to present an electron multiplier device wherein the above problems can be solved.